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Ghost Lineage
A ghost lineage is a hypothesized ancestor in a species lineage that has left no fossil evidence, but can still be inferred to exist or have existed because of gaps in the fossil record or genomic evidence. The process of determining a ghost lineage relies on fossilized evidence before and after the hypothetical existence of the lineage and extrapolating relationships between organisms based on phylogenetic analysis. Ghost lineages assume unseen diversity in the fossil record and serve as predictions for what the fossil record could eventually yield; these hypotheses can be tested by unearthing new fossils or running phylogenetic analyses. Ghost lineages and Lazarus taxa are related concepts, as both stem from gaps in the fossil record. A ghost lineage is any gap in a taxon's fossil record, with or without reappearance, while a Lazarus taxon is a type of ghost lineage wherein a species is believed to have gone extinct due to an absence of it in the fossil record, but then reappea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ichthyosauria Phylogeny
Ichthyosauria is an taxonomy (biology), order of large extinction, extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fossil evidence, they first appeared around 250 million years ago (Myr, Ma) and at least one species survived until about 90 million years ago, into the Late Cretaceous. During the Early Triassic Geologic time scale, epoch, ichthyosaurs and other Ichthyosauromorpha, ichthyosauromorphs evolved from a group of unidentified land reptiles that returned to the sea, in a development similar to how the mammalian land-dwelling ancestors of modern-day dolphins and whales returned to the sea millions of years later, which they gradually came to resemble in a case of convergent evolution. Ichthyosaurians were particularly abundant in the Late Triassic and Early Jurassic periods, until they were replaced as the top ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelacanth
Coelacanths ( ) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods (the terrestrial vertebrates including living amphibians, reptiles, birds and mammals) than to ray-finned fish. The name coelacanth originates from the Permian genus '' Coelacanthus'', which was the first scientifically named genus of coelacanths (in 1839), becoming the type genus of Coelacanthiformes as other species were discovered and named. Well-represented in freshwater and marine deposits from as early as the Devonian period (more than 410million years ago), they were thought to have become extinct in the Late Cretaceous, around 66million years ago. The first living species, ''Latimeria chalumnae'', the West Indian Ocean coelacanth, was described from specimens fished off the coast of South Africa from 1938 onward; they are now also known to inhabit the seas around the Comoro Islands off the eas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parthenogenetic
Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertilized Gametophyte, egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg. Parthenogenesis occurs naturally in some plants, algae, invertebrate animal species (including nematodes, some tardigrades, water fleas, some scorpions, aphids, some mites, some bees, some Phasmatodea, and parasitic wasps), and a few vertebrates, such as some fish, amphibians, and reptiles. This type of reproduction has been induced artificially in animal species that naturally reproduce through sex, including fish, amphibians, and mice. Normal egg cells form in the process of meiosis and are haploid, with half as many chromosomes as t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allopolyploid
Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations. The gametophyte generation is haploid, and produces gametes by mitosis; the sporophyte generation is diploid and p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ghost Population
A ghost population is a population that has been inferred through using statistical techniques. Population studies In 2004, it was proposed that maximum likelihood or Bayesian approaches that estimate the migration rates and population sizes using coalescent theory can use datasets which contain a population that has no data. This is referred to as a "ghost population". The manipulation allows exploration in the effects of missing populations on the estimation of population sizes and migration rates between two specific populations. The biases of the inferred population parameters depend on the magnitude of the migration rate from the unknown populations. The technique for deriving ghost populations attracted criticism because ghost populations were the result of statistical models, along with their limitations. Population genetics Humans In 2012, DNA analysis and statistical techniques were used to infer that a now-extinct human population in northern Eurasia had interbred with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, recognising excellence in science, supporting outstanding science, providing scientific advice for policy, education and public engagement and fostering international and global co-operation. Founded on 28 November 1660, it was granted a royal charter by Charles II of England, King Charles II and is the oldest continuously existing scientific academy in the world. The society is governed by its Council, which is chaired by the society's president, according to a set of statutes and standing orders. The members of Council and the president are elected from and by its Fellows, the basic members of the society, who are themselves elected by existing Fellows. , there are about 1,700 fellows, allowed to use the postnominal title FRS (Fellow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tachiraptor
''Tachiraptor'' ("thief of Táchira") is a genus of carnivorous theropod dinosaurs found in the early Jurassic period La Quinta Formation of Venezuela. It includes one species, ''Tachiraptor admirabilis'', described from a fossilized tibia and ischium. They were small bipedal dinosaurs, with a deduced total body length of just over . They were likely generalist predators, preying on smaller vertebrates like other dinosaurs or lizards. Discovery Since the late 1980s in the Venezuelan state of Táchira, remains of dinosaurs have been uncovered at a road-cut between La Grita and Seboruco. Most of these belonged to a small herbivore that in 2014 was described as '' Laquintasaura''. However, included in the discoveries were some theropod teeth, indicating a predator must have been present. In 2013, this was affirmed by the discovery of some theropod bones. In 2014, the type species ''Tachiraptor admirabilis'' was named and described by Max Cardoso Langer, Ascanio D. Rincón, Ja ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theropods
Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodomorpha. Theropods, both extant and extinct, are characterized by hollow bones and three toes and claws on each limb. They are generally classed as a group of saurischian dinosaurs, placing them closer to sauropodomorphs than to ornithischians. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Members of the subgroup Coelurosauria and possibly some other or all theropods were covered in feathers. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are currently represented by about 11,000 living species, making theropods the only group of dinosaurs alive today. Theropods first appeared during the Carnian age of the late Triassic period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrapod
A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all Neontology#Extant taxa versus extinct taxa, extant and Extinction, extinct amphibians and amniotes, with the latter in turn Evolution, evolving into two major clades, the Sauropsida, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (extinct pelycosaur, "pelycosaurs", therapsids and all extant mammals, including Homo sapiens, humans). Hox gene mutations have resulted in some tetrapods becoming Limbless vertebrate, limbless (snakes, legless lizards, and caecilians) or two-limbed (cetaceans, sirenians, Bipedidae, some lizards, kiwi (bird), kiwis, and the extinct moa and elephant birds). Nevertheless, they still qualify as tetrapods through their ancestry, and some retain a pair of ves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lungfish
Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton. Lungfish represent the closest living relatives of the tetrapods (which includes living amphibians, reptiles, birds and mammals). The mouths of lungfish typically bear tooth plates, which are used to crush hard shelled organisms. Today there are only six known species of lungfish, living in Africa, South America, and Australia, though they were formerly globally distributed. The fossil record of the group extends into the Early Devonian, over 410 million years ago. The earliest known members of the group were marine, while almost all post-Carboniferous representatives inhabit freshwater environments. Etymology Dipnoi is Modern Latin derived from the Greek δίπν ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not show how ancestors are related to descendants, nor does it show how much they have changed, so many differing evolutionary trees can be consistent with the same cladogram. A cladogram uses lines that branch off in different directions ending at a clade, a group of organisms with a last common ancestor. There are many shapes of cladograms but they all have lines that branch off from other lines. The lines can be traced back to where they branch off. These branching off points represent a hypothetical ancestor (not an actual entity) which can be inferred to exhibit the traits shared among the terminal taxa above it. This hypothetical ancestor might then provide clues about the order of evolution of various features, adaptation, and other e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
